Artist said: いつもアニメ塗りだったのでたまには違う塗り方をしてみたくなったので。トレスではありませんが、公式で塗り方の参考等に元にした絵があります。全然似なかったですけどねorz 元々はコミケのカタログカット用の絵を更に塗り込んだものです。
"I'm always coloring using an anime-style so I wanted to try something different. It's not traced, but I used some official art as reference for the coloring style. It didn't turn out very close to the original though... Originally this was meant for use in the Comiket catalog but I've since painted over it heavily."